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Krx-0501 reduces cognitive deficits in a saporin mouse model of Alzheimer’s disease
Lowrance SA, Matchynski JJ, Rossignol J, Dekorver N, Fink K, Salibi P, Dunbar GL (2010) Krx-0501 reduces cognitive deficits in a saporin mouse model of Alzheimer’s disease. Neuroscience 2010 Abstracts 856.8/I14. Society for Neuroscience, San Diego, CA.
Summary: Alzheimer’s disease (AD) is a progressive neurodegenerative disease marked by memory loss and dysfunction of cholinergic neurons. Neurotrophic factors, like nerve growth factor (NGF), have shown to improve cognitive function in AD patients. The inability of NGF to cross the blood brain barrier (BBB) and painful side effects have caused serious concerns over its future use as a treatment. Substituted pyrimidines, such as KRX-0501 (KRX; Keryx Biopharmaceuticals, New York, NY) on the other hand, readily cross the BBB and exert beneficial neurotrophic-like effects in vivo. In this study KRX was administered daily to mice that were given intra-cerebroventricular injections of mu p-75 Saporin (SAP; Advanced Targeting Systems, San Diego, CA) or vehicle (phosphate buffered saline). KRX treatment began at seven weeks of age and continued for 32 days. Doses were set at 10, 15, and 20mg/kg respectively. Animals were tested for cognitive impairment using the Morris water maze (MWM) task, object recognition (OR) and place recognition (PR) tasks while motor deficits were tested using MWM swim speed, rotarod (RR) and the open field (OF) tasks. On day 33 of KRX treatment, mice were sacrificed by transcardial perfusion. In a second experiment, mice received SAP or vehicle surgery and were sacrificed for enzyme-linked immunosorbent assay (ELISA) analysis. MWM results revealed significantly lower escape latencies of control animals relative to SAP animals. In addition mice treated with the low and middle doses of KRX displayed decreased escape latency on the MWM. In the OR task, only mice in the highest treatment group performed significantly above chance levels. No between group differences were seen in the PR task, swim speed, latency to fall from the RR, and distance travelled in the OF. Immunohistochemistry (IHC) using the glial fibrillary acidic protein antibody indicated that astrocyte activation took place primarily around the surgical injection sites. IHC labeling against choline-acetyltransferase revealed a significant decrease in cholinergic neurons of the medial septum. Finally, ELISA protein analysis of midbrain sections revealed that the KRX treatments did not increase levels of endogenous NGF. These results show that SAP injections produced a reproducible destruction of cholinergic neurons, accompanied by memory deficits in the MWM, in the absence of motoric deficits. The KRX treatment attenuated memory deficits, despite unabated cholinergic cell loss in the medial septum, and did so without affecting levels of endogenous NGF.
Related Products: mu p75-SAP (Cat. #IT-16)
Morphine-induced pain hypersensitivity, but not opioid tolerance, depends on microglia-mediated alteration of Cl- homeostasis in spinal dorsal horn
Ferrini F, Mattioli TAM, Lorenzo L-E, Godin A, Wiseman PW, Ribeiro-Da-Silva A, Cahill CM, Milne B, De Koninck Y (2010) Morphine-induced pain hypersensitivity, but not opioid tolerance, depends on microglia-mediated alteration of Cl- homeostasis in spinal dorsal horn. Neuroscience 2010 Abstracts 678.9/PP14. Society for Neuroscience, San Diego, CA.
Summary: Prolonged morphine exposure leads to a reduction of the antinociceptive effect (opioid tolerance) and to an increase in pain sensitivity. Recent evidences suggest that these side effects share similar mechanisms with those underlying neuropathic pain. We have shown that the release of BDNF by activated microglia following peripheral nerve injury causes a decrease in KCC2 activity in the spinal dorsal horn (DH) and weakens Cl−-mediated inhibition through GABAA and glycine receptors. Here, we tested the hypothesis that a similar cascade of events underlies morphine-induced pain hypersensitivity. Adult rats, receiving either morphine (10mg/Kg s.c. twice a day) or saline, were tested for nociceptive thresholds prior to and 1 h after morphine injections each day. Morphine induced tolerance within 2 days and hyperalgesia within 5 days. The hyperalgesia, but not the tolerance, was reversed by intrathecal (i.t.) administration of the anti-mac1 saporin-conjugated antibody (an immunotoxin targeted against microglia) or a TrkB blocking antibody, confirming involvement of both microglia and BDNF in the morphine-dependent hyperalgesia. Microglial activation was confirmed by an increased OX-42 staining after chronic morphine and was blocked by i.t. (-)-naloxone, as well as by (+)-naloxone. Interestingly, (+)-naloxone, while prevented microglia activation, had little effect on morphine tolerance. After 7 days of treatment, rats were sacrificed and DH lamina I-II neurons were recorded by imposing a Cl- load (29 mM). A depolarizing shift in EGABA was observed in lamina I neurons from morphine-treated rats (-42 ± 1 mV, n=6) compared to controls (-50 ± 2 mV, n=5, P<0.05) indicating a weaker Cl- extrusion capacity in these cells. A similar effect was also observed following 3h in vitro incubation of spinal cord slices with morphine (1 μM). No change in EGABA was observed either in the presence of opioid receptor antagonists or the TrkB blocking antibody, confirming the involvement of BDNF in the morphine-signalling pathway. Interestingly, morphine did not produce any change in EGABA in lamina II neurons. To confirm the participation of altered Cl- homeostasis on morphine-induced hyperalgesia in vivo, we administered the carbonic anhydrase inhibitor acetazolamide (i.t.) to minimize the bicarbonate-mediated component of GABAA/glycine currents. Acetazolamide was sufficient to restore inhibition in spinal DH neurons and to reverse the morphine-dependent hyperalgesia. Our data suggest that microglial activation and BDNF release following chronic morphine treatment may alter Cl- extrusion capacity of spinal lamina I neurons and increase pain hypersensitivity.
Related Products: Mac-1-SAP rat (Cat. #IT-33)
Targeting inhibitory neurons in the superficial dorsal horn: Somatostatin-saporin
Chatterjee K, Lemons LL, Wiley RG (2010) Targeting inhibitory neurons in the superficial dorsal horn: Somatostatin-saporin. Neuroscience 2010 Abstracts 585.1/XX15. Society for Neuroscience, San Diego, CA.
Summary: Intrathecal injection of somatostatin (SST), or the long-acting congener, octreotide, have been reported analgesic in humans with intractable pain. The principal SST receptor, sst2a, is expressed by GABAergic neurons in the superficial dorsal horn of the spinal cord. In the present study, we sought to determine the nocifensive behavioral effects of selectively destroying sst2a-expressing dorsal horn neurons using intrathecal injection of the targeted toxin, SST-saporin. SST-sap (500-625 ng) was injected intrathecally into rats followed by thermal plate and thermal preference shuttle box testing for up to three weeks. One of three rats injected with 625 ng of SST-sap developed severe persistent scratching of its lower body. Compared to vehicle controls and rats injected with 500 ng of corticotrophin releasing factor (CRF)-saporin, the SST-sap rats showed initially prolonged latencies and decreased nocifensive reflex responses on the 44 C hotplate that persisted for up to 17 days before returning to control levels. SST-sap rats also showed decreased reflex responses on the 0.3 C cold plate. Lastly, SST-sap rats showed no change in thermal preference in a shuttle box with floor temperatures of 15 C vs 45 C. CRF-sap rats showed delayed onset (after 8 days) of decreased hotplate responding and increased hot side occupancy in the thermal preference shuttle box. These results suggest, at the doses used, that SST-sap produced incomplete depletion of target neurons followed by compensatory plasticity, whereas, CRF-sap produced no primary effect but induced secondary plasticity resulting in long term decrease in responses to aversive heat. Higher dose studies and anatomic analysis of lesions produced by these agents are planned.
Related Products: CRF-SAP (Cat. #IT-13)
Targeting inhibitory neurons in the superficial dorsal horn: Neurotensin-saporin (NTS-sap) and neurotensin-cholera toxin A subunit (NTS-CTA)
Wiley RG, Lemons LL, Chatterjee K (2010) Targeting inhibitory neurons in the superficial dorsal horn: Neurotensin-saporin (NTS-sap) and neurotensin-cholera toxin A subunit (NTS-CTA). Neuroscience 2010 Abstracts 585.2/XX16. Society for Neuroscience, San Diego, CA.
Summary: Neurotensin (NTS) and high affinity neurotensin receptors (NTSR-1) are found in the superficial dorsal horn, primarily lamina II. Intrathecal NTS has been reported to be anti-nociceptive, naloxone does not block the anti-nociceptive effects of intrathecal NTS and NTS acting at the NTSR-1 is excitatory. Based on these facts, we hypothesized that intrathecal neurotensin produces anti-nociception by exciting inhibitory interneurons in the superficial dorsal horn. In the present study, we sought to determine the effects, on modified thermal plate responses, of lumbar intrathecal injections of NTS-saporin, that is expected to selectively kill NTSR-1-expressing dorsal horn neurons, and NTS-Cholera toxin A subunit (NTS-CTA), that is expected to excite the same neurons. NTS-sap (200-625 ng) produced sustained, remarkable, vigorous scratching of hindquarters, often to the exclusion of any other activity. 12-15 ng of NTS-sap produced no scratching and increased lick/guard responding on the 44 C hotplate. Lumbar intrathecal injections of NTS-CTA (500 ng) produced profound decrease in lick/guard responding on the 44.5 C hotplate that lasted for 100-150 hours. This unique pattern of effects is consistent with the hypothesis that NTSR-1-expressing lamina II dorsal horn neurons are both inhibitory and anti-nociceptive. These results also are consistent with the intrathecal injections of NTS-CTA producing sustained excitation of these inhibitory interneurons resulting in inhibition of nociceptive projection neurons. This strategy of exciting NTSR-1-expressing inhibitory interneurons of the superficial dorsal horn is a novel approach to achieve non-opioid-mediated analgesia which may prove valuable in treating refractory chronic pain.
Related Products: Neurotensin-SAP (Cat. #IT-56), Neurotensin-CTA (Cat. #IT-60)
Neuropeptide receptor co-expression in superficial dorsal horn: Effects of galanin-saporin, neuropeptide y-saporin and dermorphin-saporin
Lemons LL, Chatterjee K, Wiley RG (2010) Neuropeptide receptor co-expression in superficial dorsal horn: Effects of galanin-saporin, neuropeptide y-saporin and dermorphin-saporin. Neuroscience 2010 Abstracts 585.5/XX19. Society for Neuroscience, San Diego, CA.
Summary: We have previously shown that the role of specific neurons in behavioral processes can be fruitfully studied using targeted toxins. Toxins composed of a targeting neuropeptide coupled to the ribosomal-inactivating toxin, saporin, are used to selectively destroy superficial dorsal horn neurons expressing the cognate peptide receptors followed by assessment of changes in pain behavior. In the present study, we sought to compare the anatomic effects of three closely related targeted toxins, each with different nocifensive behavioral effects. Rats were given single lumbar intrathecal injections of either galanin-saporin (Gal-SAP), neuropeptide Y-saporin (NPY-SAP), or dermorphin-saporin (Derm-SAP). Lumbar spinal cord sections from each rat were stained for each of the three receptors, GalR-1, Y1R and MOR (mu opiate) using standard immunoperoxidase technique. Each toxin produced a significant decrease in staining for its cognate receptor. Gal-SAP animals showed no change in either MOR or Y1R staining. NPY-SAP rats showed decreased staining for both GalR1 and MOR, and Derm-SAP rats were assessed for changes in expression of GalR1 and Y1R. These findings suggest overlaps between the populations of neurons that express the GalR1, Y1R, and MOR. Specifically, Y1R-expressing neurons also express GalR1 and MOR, probably by separate subpopulations of Y1R neurons. The results also suggest either that Gal-SAP only kills neurons that do not express either of the other two receptors, or some of the observed loss of receptors after NPY-SAP is due to secondary (transsynaptic) effects. Double- and triple-label fluorescent immunohistochemistry will be used to directly visualize receptor co-expression patterns and targeted toxin effects. These results will be valuable in interpreting the unique nocifensive behavioral effects of each of these targeted toxins.
Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), Galanin-SAP (Cat. #IT-34), NPY-SAP (Cat. #IT-28)
Decreasing abnormal nocifensive responses in the bilateral chronic constriction injury (bCCI) model of neuropathic pain: Effects of lumbar intrathecal CCK-saporin
Datta S, Chatterjee K, Wiley R (2010) Decreasing abnormal nocifensive responses in the bilateral chronic constriction injury (bCCI) model of neuropathic pain: Effects of lumbar intrathecal CCK-saporin. Neuroscience 2010 Abstracts 175.22/MM12. Society for Neuroscience, San Diego, CA.
Summary: The bCCI model produces long lasting -cold hyperalgesia (at least 100 days) along with decreases in staining for cholecystokinin (CCK) in the dorsal horn (DH). Spinal cholecystokinin (CCK) has anti-opiate activity, and selective destruction of DH neurons expressing CCK receptors by injection of intrathecal CCK-saporin, in naïve rats decreases thermal nocifensive reflex responses and is additive with morphine in decreasing nocifensive responses to heat. In the present study, we sought to determine the effects of intrathecal CCK-sap in the bCCI model of neuropathic pain in Long Evans female rats. bCCI rats underwent bilateral ligation of the sciatic nerves with chromic gut sutures. Controls underwent sham surgery with no ligation. Rats were tested on 0.3 C cold plate, thermal preference task (TPT) (shuttle box with floor temperatures of 15 C vs 45 C) and mechanical stimulation (von Frey). bCCI produced increased responses on the cold plate. 21 days after the bCCI surgery, the rats were injected with 1500 ng CCK-sap into the lumber CSF. Then, thermal and mechanical testing was repeated at intervals. Intrathecal CCK-sap injections decreased abnormal nocifensive responding of bCCI rats on the cold plate. CCK-sap reduced withdrawal responses to mechanical stimulation in bCCI rats. In TPT testing, the bCCI animals were hyperalgesic to cold (reduced cold side occupancy). After intrathecal CCK-sap injections, thermal preference was reversed (increased cold side occupancy). We interpret these results as showing that CCK-sap reverses abnormal nocifensive responses of bCCI in rats to aversive cold and mechanical stimuli. These results suggest that silencing CCK receptor-expressing superficial DH neurons is a potential strategy for development of new treatments for chronic neuropathic pain.
Related Products: CCK-SAP (Cat. #IT-31)
Gastrin-releasing peptide receptor in the spinal cord mediates mechanical allodynia following nerve injury
Li C, Back S, Lee J, Baek SK, Na H (2010) Gastrin-releasing peptide receptor in the spinal cord mediates mechanical allodynia following nerve injury. Neuroscience 2010 Abstracts 176.2/OO4. Society for Neuroscience, San Diego, CA.
Summary: Gastrin-releasing peptide receptor (GRPR) has been suggested as an itch-specific gene in the spinal cord (Sun et al., Nature, 2009). They described that selective ablation of GRPR-expressing lamina I neurons led to deficits in itch-related scratching behaviors without any effects on pain behaviors including nerve injury-induced mechanical allodynia. It has been known that two types of mechanical allodynia, such as static and dynamic allodynia, can be detectable in neuropathic patients, and may be mediated by distinct mechanisms. In the present study, we investigated the role of spinal GRPR in each of static and dynamic allodynia using both rat- and mouse-tail models of neuropathic pain. Bombesin-saporin (bombesin-sap) was administered intrathecally to ablate spinal GRPR-expressing neurons. Scratching behaviors evoked by pruritogenic agents, such as serotonin and chloroquine, and physiological pain behaviors were analyzed before nerve injury. Static or dynamic allodynia was assessed by the application of von Frey filaments to the tail or brushing the tail with a filament, respectively. RC3095, a GRPR antagonist, was given intrathecally to see its effects on static and dynamic allodynia in neuropathic rats. Bombesin-sap treatment resulted in reduction of GRPR-immunoreactive cells in lamina I of spinal dorsal horn and scratching deficits. Physiological pain behaviors of these animals were not different from those of control animals. Following the partial injury of tail-innervating nerves, animals treated with bombesin-sap exhibited comparable dynamic allodynia to control one. However, they failed to manifest static allodynia during the entire experimental period. In addition, RC3095 relieved static, but not dynamic, allodynia. These findings suggest that spinal GRPR mediates nerve injury-induced static mechanical allodynia as well as itching sensation in normal state.
Related Products: Bombesin-SAP (Cat. #IT-40)
Featured Article: Targeted ablation of sympathetic neurons reduces ventricular arrhythmias and autonomic dysreflexia
Lujan HL, DiCarlo SE (2010) Featured Article: Targeted ablation of sympathetic neurons reduces ventricular arrhythmias and autonomic dysreflexia. Targeting Trends 11(4)
Related Products: CTB-SAP (Cat. #IT-14)
Read the featured article in Targeting Trends.
See Also:
- Lujan HL et al. Targeted Ablation of Cardiac Sympathetic Neurons Reduces the Susceptibility to Ischemia-Induced Sustained Ventricular Tachycardia in Conscious Rats. Am J Physiol Heart Circ Physiol 298:H1330-H1339, 2010.
- Lujan HL et al. Targeted Ablation of Mesenteric Projecting Sympathetic Neurons Reduces the Hemodynamic Response to Pain in Conscious Spinal Cord Transected Rats. Am J Physiol Regul Integr Comp Physiol 298(5):R1358-1365, 2010.
NK-1-receptor-mediated lesion of spinal post-synaptic dorsal column neurons might improve intractable visceral pain of cancer origin.
Wang Y, Mu X, Liu Y, Zhang X, Wu A, Yue Y (2011) NK-1-receptor-mediated lesion of spinal post-synaptic dorsal column neurons might improve intractable visceral pain of cancer origin. Med Hypotheses 76(1):102-104. doi: 10.1016/j.mehy.2010.08.042
Summary: There is evidence that spinal post-synaptic dorsal column neurons begin to express neurokinin-1 receptors after visceral stimulation. The authors discuss using this expression profile to target SSP-SAP (Cat. #IT-11) to these neurons and eliminate them. This use of ‘molecular neurosurgery’ may be a replacement for traditional neurosurgery for the treatment of cancer-related visceral pain.
Related Products: SSP-SAP (Cat. #IT-11)
Hyperalgesic priming is restricted to isolectin B4-positive nociceptors.
Joseph EK, Levine JD (2010) Hyperalgesic priming is restricted to isolectin B4-positive nociceptors. Neuroscience 169(1):431-435. doi: 10.1016/j.neuroscience.2010.04.082
Summary: Hyperalgesic priming is an injury that induces a chronic pain state marked by the presence of inflammatory cytokines. The authors evaluated which populations of nociceptors are involved in the priming process. Rats that received 3.2 µg intrathecal injections of IB4-SAP (Cat. #IT-10) failed to establish priming. Acute mechanical hyperalgesia could still be induced, indicating that IB4+ nociceptors are necessary for priming, but a different nociceptor group is involved with nociceptor sensitization.
Related Products: IB4-SAP (Cat. #IT-10)